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02 ranger rough idle.

TexasNomad

FTFS Designated DRINKER!
Hey guys my ranger is acting up a bit, when its sitting and idling the tach will drop a bit and the engine will all most sound like its going to die but then but picks up up and runs fine again.
This is what i've done to it.
Clean filter new plugs new wires new fuel new PCV valve all vac lines checked for leaks crimps or signs of damage.
No codes being thrown and i'm out of idea's.
Thanks guys :D
 

CowboyBilly9Mile

Charter Member
7,118
442
USA
Hey guys my ranger is acting up a bit, when its sitting and idling the tach will drop a bit and the engine will all most sound like its going to die but then but picks up up and runs fine again.
This is what i've done to it.
Clean filter new plugs new wires new fuel new PCV valve all vac lines checked for leaks crimps or signs of damage.
No codes being thrown and i'm out of idea's.
Thanks guys :D

Sometimes IAC solenoids get a little dirty; it wouldn't hurt to try cleaning it. And BTW, did this by chance start after you bought gas?
 

blacksnapon

Moderator
Staff member
FORD: 2000-2003 TAURUS
2002 THUNDERBIRD
2000-2003 EXPLORER, RANGER
2001-2003 EXPLORER SPORT TRAC, EXPLORER SPORT
LINCOLN: 2000-2002 LS
MERCURY: 2000-2003 SABLE, MOUNTAINEER


ISSUE:
Some vehicles, may exhibit drivability conditions. These may include:

No start
Difficult to start
Stall
Low idle
Rough idle
High idle
Hesitation/surge while accelerating or at steady speed
These conditions may be intermittent with no Diagnostic Trouble Codes (DTC) and no Malfunction Indicator Lamp (MIL). In some cases DTC and MIL may be evident.

ACTION:
Trouble cannot be identified with 95% of returned Idle Air Control (IAC) valves. The following procedure is supplemental information to normal diagnostics to facilitate accurate identification of malfunctioning valves. These symptoms would include engine stall, hard start, crank/no start, idling problems, and Idle Speed Control System related DTC's.



Perform normal diagnostics.

SERVICE INFORMATION



IAC DIAGNOSTIC SERVICE TIPS - GENERAL

Never clean an IAC valve. Carburetor cleaners and other cleaning agents may temporarily repair the drivability concern, but the long-term functionality of the valve is compromised.

For all drivability concerns, make certain the service writer obtains as much information as possible from the customer as to the conditions causing drivability concern. Attached is a drivability concern check off sheet (Figure 2) that if used, can help reduce the time required to diagnose a vehicle.

NOTE: IF THE ENGINE STALLED WHILE THE VEHICLE WAS IN GEAR AND MOVING THE POSSIBILITY OF THE IAC VALVE CAUSING THIS IS UNLIKELY UNLESS IT OCCURRED ON DECELERATION.



Use the following Supplemental information for 3.0L 4V Duratec Engines, in the Taurus/Sable, and Lincoln LS.

Use the following conditions for the test described below:
Transmission in park
Engine temperature should be at least 190° F (88° C)
All accessories should be off steering wheel in the center position
EGVR and EVAPDUTY CYCLE at zero, if the vehicle has an EGR system
Short and long term fuel trims less than 15%
At stabilized engine speed (RPM) and temperature (hot idle) per the Powertrain Control Emission Diagnostics (PC/ED) manual, verify the IAC duty cycle is within reference values called out in the following chart in this TSB.
NOTE: IT IS USUAL TO SEE THE IAC DUTY CYCLE VARY BY 1% TO 2% OVER SEVERAL MINUTES.




Use the following Supplemental information for 4.0L SOHC Engines in the Ranger, Explorer, Mountaineer, Explorer Sport and Explorer Sport Trac.

If no DTC's present check the following items in this order before examining the IAC valve:

BARO Hz reading - Refer to Barometric Pressure Chart listed in this TSB
Battery and fuse box power lead
Ground wire attachments
Wiring (wiggle test)
PCM voltage
Vacuum leaks
Examine IAC valve under these conditions:

PCM updated to the latest available calibration
Transmission in park
Warm stabilized vehicle with engine temperature at least 190° F (88° C)
All accessories and cooling fan should be off
Steering wheel in the center position
EGVR and EVAPDC at zero, if the vehicle has an EGR system
Short and long term fuel trims (less than 15)
Perform the following steps in order:

Using either NGS or WDS bring up the following PIDS: IACTRIM, IACKAM2, IACKAM3.
Allow vehicle to idle until the IACTRIM PID is 0.
NOTE: IACTRIM ALWAYS TRIES TO GO TO 0. WHEN MOVING TOWARDS 0, THE IACKAM2 PID SHOULD BE CHANGING. IF IACKAM3 IS CHANGING, THEN THE AIR CONDITIONING SHOULD BE TURNED OFF.



If IACKAM2 is between -0.35 and +0.35 with IACTRIM=0, then the valve is operating properly at idle. The remainder of this TSB will help diagnose true root cause.
If IACKAM2 is not between -0.35 and +0.35, it is highly likely that the engine idle system (to include the throttle body and air intake system) is not operating properly.
NOTE: FOR ALL VEHICLES PLEASE RECORD THE OBSERVED IAC DUTY CYCLE AND ENGINE RPM IN THE WARRANTY CLAIMS COMMENTS FOR THIS DIAGNOSTIC.



IAC Diagnostic Service Tips - DTC 1506 (IAC Over Speed Error) and other High Idle Concerns:

There are two primary causes of high idle:
Damaged IAC valves and
Vacuum leaks
IAC valves can be damaged from engine induction backfires. Many times the customer may not notice the induction backfire but will notice the high idle afterwards. Indications of valve damage can be a shiny, almost polished appearance in the interior of the valve and a dislocated pintle. An IAC valve damaged by backfire should be replaced. Refer to Figure 1.
Inspect PCV system for leaks especially looking for cracks along any rubber elbow joints; also verify that the correct PCV valve is installed.
Inspect for vacuum hoses loose or disconnected from intended ports and connections. Induction backfire can loosen or disconnect vacuum hoses.
Two indicators can help you identify if a vacuum leak is present, even if the engine RPM appear normal in the service bay. If the duty cycle is below specification that is indicative that the engine is receiving too much air (from a vacuum leak) and the PCM is ordering the valve to close up to restrict flow. Another indication is fuel trim. Record the long term and short term fuel trim PIDS (LONGFT1, LONGFT2, SHORTFT1, etc.), if short term fuel trims are high (above specification) this is a possible indication of a vacuum leak, making the engine run lean, and the PCM is attempting to compensate.
IAC Diagnostic Service Tips - DTC 1507 (IAC Under Speed Error) and Other Low Idle Concerns:

An under speed error may not necessarily be a fault with the IAC valve. A large friction load on the engine or obstruction in the air intake system could also reduce the engine RPMs.
There are four possible sources of friction load that can contribute to under speed error or low idle concerns.
Power Steering Load
Air Conditioning Load
Electrical Load
Automatic Transmission Torque Converter Load
IAC Diagnostic Service Tips - Rough Idle Concerns:

Rough idle concerns are often a result of a lean running condition
Another possible cause is contamination build up on the MAF sensor
IAC Diagnostic Service Tips - Engine Hard Start/Engine Crank-No Start

While performing diagnostics, the technician should ensure that the fuel system is working correctly for all engines with hard start/crank no-start complaints.
When diagnosing a mechanical return less fuel system, the following correction to the PC/ED pinpoint HC (4) diagnostic procedure should be used when performing the KEOE fuel pressure test:
Perform the KOEO fuel pressure test as specific in the PC/ED manual.
The fuel pressure should drop off no more than 10 psi from maximum pressure (no lower than 55 psi for a 65 psi max system or no lower than 45 psi for a 55 psi max system) within 5 minutes of the start of the test.
The fuel pressure should drop off to no less than 30 psi within 30 minutes of the start of the test.
For greatest accuracy, the service technician should read the fuel pressure as soon as possible after pump shut off, no more than 5 minutes after the start of the test.
NOTE: RETURNABLE AND ELECTRONIC RETURN LESS SYSTEMS SHOULD ALSO BE DIAGNOSED USING THE PROCEDURES LISTED FOR THEM IN PINPOINT TEST HC.



IAC Diagnostic Service Tips - High Idle RPM at Start Up:

Most engines will have a temporary high idle at engine start up to allow for catalyst light off. If DTC 1506 is not present, this indicates that there is no fault present with the IAC.
A vehicle with very low odometer miles, may exhibit a higher than normal temporary startup fast idle (1600-2500 RPM that decreases slowly). No repairs should be attempted because this is a normal temporary PCM calibration strategy to prevent spark plug fouling during plant/transportation operation. The calibration will permanently revert to its normal strategy after the PCM has seen its first 4 miles of continuous drive cycle. A brand new vehicle may accumulate some mileage without turning this strategy off if the drive cycle has been below 4 miles at a time.
IAC Diagnostic Service Tips - IAC Valve Noise Issues

For IAC valve noise concerns check for obstructed or potentially damaged IAC valve from backfire.

NOTE: ON SOME NEWER MODEL YEAR VEHICLES THE REACTION SPEED OF THE IAC VALVE IS FAST ENOUGH THAT IT MIGHT MAKE A "POPPING" SOUND AS IT REACTS TO A LARGE IDLE LOAD. THIS IS A NORMAL CHARACTERISTIC AND NO ATTEMPTS SHOULD BE MADE IN AN EFFORT TO MODIFY THE PERFORMANCE OF THE IAC VALVE. IF POSSIBLE, COMPARE AGAINST A LIKE VEHICLE.






NOTE: REMEMBER THAT MOST WEATHER SERVICES REPORT A LOCAL BAROMETRIC PRESSURE THAT HAS BEEN CORRECTED TO SEA LEVEL. THE BARO PID, ON THE OTHER HAND, REPORTS THE ACTUAL BAROMETRIC PRESSURE FOR THE ALTITUDE THE VEHICLE IS BEING OPERATED IN. LOCAL WEATHER CONDITIONS (HIGH AND LOW PRESSURE AREAS) WILL CHANGE THE LOCAL BAROMETRIC PRESSURE BY SEVERAL INCHES OF MERCURY (±3 Hz, ±1 in. Hg.).



NOTE: BARO IS UPDATED ONLY WHEN THE VEHICLE IS AT HIGH THROTTLE OPENINGS. THEREFORE, A VEHICLE, WHICH IS DRIVEN DOWN FROM A HIGHER ALTITUDE MAY NOT HAVE HAD AN OPPORTUNITY TO UPDATE THE BARO VALUE IN KAM. IF YOU ARE NOT CONFIDENT THAT BARO HAS BEEN UPDATED, PERFORM THREE OR FOUR HEAVY, SUSTAINED ACCELERATIONS AT GREATER THAN HALF-THROTTLE TO ALLOW BARO TO UPDATE.
 

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